Methods and apparatus for power saving in discontinuous reception—adaptive neighbor cell search duration

ABSTRACT

Methods and apparatus for adaptively adjusting temporal parameters (e.g., neighbor cell search durations). In one embodiment, neighbor cell search durations during discontinuous reception are based on a physical channel metric indicating signal strength and quality (e.g. Reference Signal Received Power (RSRP), Received Signal Strength Indication (RSSI), Reference Signal Receive Quality (RSRQ), etc.) of a cell. In a second embodiment, neighbor cell search durations are based on a multitude of physical layer metrics from one or more cells. In one variant, the multitude of physical layer metrics may include signal strength and quality metrics from the serving base station as well as signal strength and quality indicators from neighbor cells derived from the cells respective synchronization sequences.

PRIORITY AND RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Ser. No.61/593,202 filed Jan. 31, 2012 and entitled “METHODS FOR POWER SAVING INDISCONTINUOUS RECEPTION—ADAPTIVE NEIGHBOR CELL SEARCH DURATION”, whichis incorporated herein by reference in its entirety.

This application is also related to U.S. Provisional Patent ApplicationSer. Nos. 61/585,207 entitled “Method for Power Saving in DiscontinuousReception of Wireless Receiver—Adaptive Wake-up” filed Jan. 10, 2012,61/585,209 entitled “Method for Power Saving in Discontinuous Receptionof Wireless Receiver—Staggered Measurement” filed Jan. 10, 2012, and61/587,092 entitled “Method for Power Saving in Discontinuous Receptionof Wireless Receiver—Adaptive Receiver Mode Selection” filed Jan. 16,2012, each of the foregoing being incorporated herein by reference inits entirety.

COPYRIGHT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND 1. Technological Field

The present disclosure relates generally to the field of wirelesscommunication and networks. More particularly, the present disclosure isdirected, inter alia, to methods and apparatus for managing andimproving power saving during discontinuous reception.

Other features and advantages of the present disclosure will immediatelybe recognized by persons of ordinary skill in the art with reference tothe attached drawings and detailed description of exemplary embodimentsas given below.

SUMMARY

The present disclosure satisfies for the aforementioned needs byproviding, inter cilia, improved methods and apparatus managing andimproving power saving during discontinuous reception.

Firstly, a method for adaptively managing a parameter of a mobile deviceis disclosed. In one embodiment, the method includes: initializing aseries of criteria, the series of criteria used at least in part tomanage the parameter; obtaining measurements useful in the adaptivemanagement of the parameter; comparing the measurements againstrespective ones of the series of criteria; determining based at least inpart on the comparison if the parameter needs updating; and updating theparameter if it is determined that said parameter needs updating.

A mobile device having enhanced power management is disclosed. In oneembodiment, the mobile device comprises a user equipment (UE) capable ofoperation within a cellular (e.g. LTE) network, and comprises logicconfigured to implement a parameter adjustment based on a series ofcriteria.

A computer readable apparatus is disclosed. In one embodiment, theapparatus comprises a storage medium having at least one computerprogram disposed thereon, the at least one program being configured to,when executed, implement management of discontinuous channel operationso as to enhance power saving within, e.g. a mobile device.

An integrated circuit (IC) is disclosed. In one embodiment, theintegrated circuit comprises logic which is configured to implementmanagement of discontinuous channel operation so as to enhance powersaving within, e.g., a mobile device.

A wireless system is disclosed. In one embodiment, the system includes aplurality of base stations and a plurality of mobile user devices. Themobile user devices are configured to implement management ofdiscontinuous channel operation so as to enhance power saving.

A method for adaptively managing a search duration of a mobile device isdisclosed. In one embodiment the method includes establishing one ormore sets of threshold values; establishing a set of search durations;providing at least one indication of one or more physical qualities of acommunication signal; determining based at least on part of the one ormore physical qualities if the at least one indication is withinrespective the one or more sets threshold values; and updating a searchduration using the set of search durations based on the determination.

A base station apparatus capable of enhanced power management of mobiledevices is disclosed. In one embodiment, the base station is configuredto adaptively control the cell search duration of mobile devices withinthe cellular network so as to enhance power saving of the mobiledevices.

Other features and advantages will immediately be recognized by personsof ordinary skill in the art with reference to the attached drawings anddetailed description of exemplary embodiments as given below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of one exemplary Long TermEvolution (LIE) cellular network useful with various aspects of thepresent disclosure.

FIG. 2 is a logical flow diagram illustrating one embodiment of thegeneralized method of configuring physical parameters according to thepresent disclosure.

FIG. 2A is a logical flow diagram illustrating one exemplaryimplementation of the method of FIG. 2 in the context of searchduration.

FIG. 3 is a graphical representation of one exemplary set first andsecond thresholds and durations according to the present disclosure.

FIG. 4 is a graphical representation of a LTE radio frame useful withvarious aspects of the present disclosure.

FIG. 4A is a graphical representation of a LTE radio frames includingsynchronization sequences useful with various aspects of the presentdisclosure.

FIG. 5 is a logical block diagram of a generalized correlation mechanismto detect synchronization signal useful with various aspects of thepresent disclosure.

FIG. 6 is a logical flow diagram illustrating one embodiment of thegeneralized method of improving power consumption during discontinuousreception according to the present disclosure.

FIG. 6A is a logical flow diagram illustrating one exemplaryimplementation of the method of FIG. 6.

FIG. 7 illustrates one embodiment of an apparatus in accordance with thepresent disclosure.

All Figures © Copyright 2012-2013 Apple Inc. All rights reserved.

DETAILED DESCRIPTION

Reference is now made to the drawings, wherein like numerals refer tolike parts throughout.

Exemplary embodiments of the present disclosure are now described indetail. While these embodiments are primarily discussed in the contextof cellular networks including without limitation, third generation (3G)Universal Mobile Telecommunications System (UMTS) wireless networks,Worldwide Interoperability for Microwave Access (WiMAX), Long TermEvolution (LTE) wireless networks, and other fourth generation (4G) orLTE-Advanced (LTE-A) wireless networks, it will be recognized by thoseof ordinary skill that the present disclosure is not so limited. Infact, the various features of the disclosure are useful in and readilyadapted to any wireless network that can benefit from the adaptivesearch procedures described herein.

Overview

In many existing cellular networks, the concept of discontinuousreception (DRX) has been utilized in order to save on power consumptionand improve the battery life of wireless user equipment (UE) (e.g. cellphones, smartphones, tablets, etc.). DRX powers down most of the UEcircuitry when there are no packets to be received or transmitted, andonly wakes up the UE to listen to the network at specified times.

During DRX, one important task for the UE is to perform necessarymeasurements of neighbor cells for UE cell reselection in RRC_IDLE modeor reporting to the active base station (BS) for the BS's handoverdecisions in RRC_CONNECTED mode. However, neighbor cells have to besearched and detected before the measurements can be taken. The UE, uponentering a wake-up state, attempts to detect neighbor cells byperforming synchronization attempts on the periodic samples of thesequences transmitted by the neighbor cells. The UE may perform repeatedsynchronization attempts in order to provide for higher reliability ofdetection of the neighbor cells. The process of repeating such attemptscan contribute to a significant portion of UE wake-up time, requiringincreased power consumption by the UE.

To address this and other problems, various embodiments of the presentdisclosure implement adaptive solutions, including for example adjustingthe number of synchronization attempts, and/or the used samples, inorder to detect neighbors based on physical layer metrics so as toprovide adequate reliability of detection while minimizing the requisitepower consumption by the UE.

Power Consumption and Management in Cellular Networks

In the following discussion, a cellular radio system is described thatincludes a network of radio cells each served by a transmitting station,known as a cell site or base station (BS). The radio network provideswireless communications service for a plurality of user equipment (UE)transceivers. The network of BSs working in collaboration allows forwireless service which is greater than the radio coverage provided by asingle serving BS. The individual BSs are connected to a Core Network,which includes additional controllers for resource management and insome cases access to other network systems (such as the Internet, othercellular networks, etc.).

FIG. 1 illustrates one exemplary Long Term. Evolution (LTE) cellularnetwork 100, with user equipments (UEs) 102, operating within thecoverage of the Radio Access Network (RAN) provided by a number of basestations (BSs) 104. The LTE base stations are commonly referred to as“Enhanced NodeBs” (eNBs). The Radio Access Network (RAN) is thecollective body of eNBs along with the Radio Network Controllers (RNC).The user interfaces to the RAN via the UE, which in many typical usagecases is a cellular phone or smartphone. However, as used herein, theterms “UE”, “client device”, and “user device” may include, but are notlimited to, cellular telephones, smartphones (such as for example aniPhone™ manufactured by the Assignee hereof), personal computers (PCs),such as for example an iMac™, Mac Pro™, Mac Mini™ or MacBook™, andminicomputers, whether desktop, laptop, or otherwise, as well as mobiledevices such as handheld computers, PDAs, personal media devices (PMDs),such as for example an iPod™, or any combinations of the foregoing.

Each of the eNBs 104 are directly coupled to the Core Network 106; e.g.,via broadband access. Additionally, in some networks, the eNBs maycoordinate with one another, via secondary access channels. The CoreNetwork provides both routing and service capabilities. For example, afirst UE connected to a first eNB can communicate with a second UEconnected to a second eNB, via routing through the Core Network.Similarly, a UE can access other types of services e.g., the Internet,via the Core Network.

In order to reduce power consumption and improve the battery life ofwireless user equipment (UE), certain wireless technologies implementso-called “discontinuous reception” (DRX) and “discontinuoustransmission” (DTX). During DRX and DTX operation, the UE powers downmost of the radio transceiver circuitry when there are no packets to bereceived or transmitted. The powered down components (in “sleep mode”)are powered up (“wake-up”, “warm-up”) at designated time intervals toe.g., receive data from the network (“listening”). During wake-up, theUE needs to prepare the radio transceiver for reception by e.g.,synchronizing the UE in time and frequency to the BS, allowing feedbackloops to settle, etc. Use of DRX and DTX greatly improves device standbytime, and can also provide significant reductions in power consumptionduring low-use scenarios.

DRX can be enabled in different network connection states; these networkconnection states include when the UE has a radio resource connection(RRC), and when the UE is idle. During connected mode DRX operation, theUE listens to downlink (DL) packets that follow a specific identifyingpattern (e.g., packet header, etc.) that has been determined by thebase-station (BS). In contrast, during idle mode DRX operation, the UEperiodically looks for a paging message from the BS to determine if theUE needs to connect to the network and acquire the uplink (UL) timing.Within the exemplary context of LTE networks, DRX mode operation isspecified for two distinct states: (i) RRC_CONNECTED, and (ii) RRC_IDLE.

In the RRC_CONNECTED state, DRX mode is enabled during an idle period ofthe downlink (DL) packet arrival. In the RRC_IDLE state, the UE must bepaged for DL traffic (according to a paging schedule) or initiate uplink(UL) traffic by requesting a RRC connection with the serving eNB.

Currently, DRX and DTX techniques are used in several wirelesstechnologies including, for example Universal Mobile TelecommunicationsSystem (UMTS), LTE (Long-term Evolution), and WiMAX (WorldwideInteroperability for Microwave Access). Incipient technologies willsupport very high data rates by using techniques that consumesignificant amounts of power during operation. Consequently, reducingtransceiver use during inactivity will greatly improve overalltransceiver power consumption. Existing schemes for DRX are controlledby the BS; i.e., the BS determines the times during DRX transmissionsare sent from the BS to the UE; however, the UE independently managesits wake-up procedure to ensure that it will receive these DRXtransmissions.

Additionally, during DRX mode, one important task is to performnecessary measurement of neighbor eNBs for UE cell reselection inRRC_IDLE state or reporting to the serving BS for the BS's handoverdecisions in RRC_CONNECTED state. Neighbor eNBs have to be searched anddetected before measurements can be taken. The UE detects neighbor eNBbased on synchronization signals sent periodically by the eNBs. The UEmay perform repeated synchronization attempts to provide higherreliability in detecting neighbor eNBs. In DRX mode, the synchronizationcan contribute significantly to the UE wake time.

After the eNBs have been searched and detected, dependent on the radioaccess technology (RAT) of the eNBs being measured, there are four typesof cell measurements performed by the exemplary UE. The first type ofmeasurement is a serving-cell measurement, which is a measure of thesignal strength of the serving cell that the UE is “camped” on. Theserving-cell measurement is typically measured more often compared toother measurements. For example, in LTE, the serving-cell measurement isrequired to be measured at least once every DRX cycle.

The second type of measurement is the measurement of intra-frequencycells. This measurement is typically initiated by the when the servingcell's reference signal receive power (RSRP) or reference signalreceived quality (RSRQ) fall below their respective threshold.

The third measurement is the measurement of inter-frequency cell. The UEis required to detect and measure the relevant measurement quality forinter-frequency LTE neighbors based on network threshold configuration.

The fourth type of measurement is the measurement of inter-RAT cells.Inter-RAT cell measurement can take place if the quality of the servingcell/BS is above a high priority threshold, the UE search higherpriority inter-RAT frequency layers with certain periodicity. If theserving cell quality is less than another threshold the UE searches andmeasures all inter-RAT cells on the configured measurement frequencies.

Methods

FIG. 2 illustrates one embodiment of a method 200 for improving powerconsumption during discontinuous reception using a physical channelmetric according to the disclosure. The method adjusts a parameter (suchas e.g., search window period) according to criteria associated with thephysical channel(s) of the serving cell/base station (BS).

Referring to FIG. 2, at step 202 of the method 200, the UE initializesneighbor cell search parameters used to adaptively change the parameterof interest.

In the exemplary embodiment of FIG. 2, separate criteria are maintainedfor increasing or decreasing the parameter of interest. An advantage ofmaintaining separate criteria for increasing or decreasing the neighborcell parameters is that if a measurement is consistently made around aparticular criterion, it would be possible for the parameter (e.g.,search duration) to frequently oscillate or dither between two searchdurations in implementations of only a single set of criteria forincreasing or decreasing the parameter. By maintaining separatecriteria, one can account for a sufficient increase or decrease in themeasured value before changing the parameter.

Referring back to FIG. 2, at step 204, the UE will obtain (e.g., takeitself, or receive from another source) physical layer measurements froma BS in communications range with the UE.

At step 206, the UE will determine if the physical layer measurementsmeet a/the first criterion/criteria. If the measured value meets thecriterion, no adjustment in the neighbor cell parameter (e.g., searchduration) is required and the method proceeds to step 212. If thecriterion is not met, it is an indication that reliability ofindentifying neighbor cells may be compromised using the currentneighbor cell parameter, and that the parameter should be adjusted toprovide adequate reliability. The new neighbor cell parameter(s) is/aredetermined in step 208.

At step 208, the UE will determine if the physical layer measurementmeets the first criterion/criteria. After this determination has beenmade, the method proceeds to step 210.

At step 210, the UE will update the neighbor cell search parameters.After the neighbor cell search parameters have been updated, the UE mayproceed back to step 204.

Proceeding to step 212, the UE will determine if the physical layermeasurements meet a second criterion/criteria. If the measurement ismeets the criterion, it is deemed to be of sufficient quality to adjustthe parameter while maintaining a determined level of reliability incell identification. The method then proceeds to step 214.

At step 214 of method 200, the UE will determine if the physical layermeasurement meets the second criterion/criteria. If the criterion ismet, then the method proceeds to step 216.

At step 216, the UE will update the neighbor cell search parameters.After the neighbor cell search parameters have been updated, the UE mayproceed back to step 204.

At step 218, after a determination that the physical channel measurementdid meet the first criterion (per step 236) and not the second criterion(per step 212), the UE does not update the neighbor cell parameter(s).The method then proceed back to step 204.

FIG. 2 a illustrates one more specific embodiment 230 of the generalizedmethod 200 for improving power consumption during discontinuousreception using a physical channel metric indicating signal strength andquality, according to FIG. 2. In one aspect, the method adjusts a searchwindow period according to the quality of signal received from theserving cell/base station (BS). Specifically, a user equipment (UE) orother device can configure the search window duration for performingsynchronization attempts with neighbor cells by comparing the ReferenceSignal Receive Quality (RSRQ) of the serving BS, as measured by the UE,against a variety of preset RSRQ threshold limits.

Referring to FIG. 2 a, at step 232 of the method 230, the UE initializesneighbor cell search parameters used to adaptively change the searchwidow duration. In one such variant, a discrete set S, with a set sizeN, of possible neighbor cells search durations (NCSDUR) is selected inascending order ranging from the shortest allowable NCSDUR time and thelongest allowable NCSDUR time. In addition, two sets of RSRQ thresholdvalues are established which indicate RSRQ values used in determiningwhether to increase or decrease the NCSDUR. The first set of RSRQthreshold values (RSRQ_Threshold_(low)) arranged in descending order areused to determine when the UE will select a particular NCSDUR of alonger duration than the current NCSDUR. The second set of RSRQthreshold values (RSRQ_Threshold_(high)) arranged in descending are usedto determine when the UE will select a particular NCSDUR of a shorterduration compared to the current NCSDUR being used. BothRSRQ_Threshold_(low) and RSRQ_Threshold_(high) sets of threshold valueshave a set size of N−1, (i.e., set size one less than set size S). Theindex (i) of the sets are initialized at the first value of the set(i.e. i=0) according to Equation (1), Equation (2), and Equation (3) asset forth below.NCSDUR=S(i);  (Equation 1)RSRQ_(low)=RSRQ_Threshold_(low)(i);  (Equation 2)RSRQ_(high)=RSRQ_Threshold_(high)(i);  (Equation 3)

FIG. 3 is a graphical illustration of the exemplary sets of NCSDUR,RSRQ_Threshold_(low), and RSRQ_Threshold_(high) values. In one variantof the method of the present disclosure, the RSRQ_Threshold_(low), andRSRQ_Threshold_(high) are sets of RSRQ threshold values in dBm, whileNCSDUR are set in durations of milliseconds (ms). As noted above withrespect to FIG. 2, an advantage of maintaining separate criteria (here,threshold values) for increasing or decreasing the neighbor cell searchduration period is that if a RSRQ is consistently measured around aparticular threshold value, it would be possible for the search durationto frequently oscillate or dither between two search durations inimplementations of only a single set of thresholds for increasing ordecreasing the search duration. By maintaining separate sets ofthreshold values, one can account for a sufficient increase or decreasein RSRQ before changing a search duration.

Referring back to FIG. 2 a, at step 234, the UE will obtain (e.g., takeitself, or receive from another source) physical layer measurements froma BS in communications range with the UE. In one embodiment, the UE willmeasure and calculate the RSRQ of the serving BS when the UE is inCONNECTED mode. As a brief aside, RSRQ is the ratio between theReference Signal Received Power (RSRP) and the Received Signal StrengthIndicator (RSSI). While RSRP is the average of the power of all thedownlink reference signals (RS) across the entire bandwidth from aspecific-cell to determine the signal strength of that respective cell,RSRP gives no indication of signal quality. The exemplary receivedsignal strength indicator (RSSI) parameter is the total received signalpower from the serving cell, including all interference and thermalnoise. By comparing the RSRP against RSSI, RSRQ provides an indicationof signal quality and power received from the serving BS. Thus, by theUE monitoring RSRQ, the adaptive neighbor cell search duration mayaccount for both received signal power level of the serving base stationand amount of received interference in decision making.

At step 236, the UE will determine if the physical layer measurementsare within a first threshold. In one exemplary embodiment, the measuredRSRQ is compared against RSRQ_(low). If the RSRQ is a larger value thanthe RSRQ_(low) threshold value, no increase in the neighbor cell searchduration is required and the method proceeds to step 242. If the RSRQ isbelow RSRQ_(low), it is an indication that reliability of indentifyingneighbor cells may be compromised using the current neighbor search cellduration and that the duration should be increased to provide adequatereliability. The increase in neighbor cell search duration is determinedin step 238.

At step 238, the UE will determine whether the physical layermeasurement is located within in the first set of a range of thresholds.In one embodiment, the UE searches the set of RSRQ_Threshold_(low) tofind index i that satisfies Equation (4).RSRQ_Threshold_(low)(i+1)<RSRQ≦RSRQ_Threshold_(low)(i)  (Equation 4)

By searching the set of RSRQ_Threshold_(low) values, the UE candetermine how many thresholds have been exceeded by the low RSRQmeasurement in order to properly update the neighbor cell searchduration window. If no value of i satisfies Equation (4), it is anindication that RSRQ is lower than lowest RSQP_Threshold_(low) value,thus i is set to the lowest possible RSQP_Threshold_(low) which isi=(N−1). Note that the NCSDUR will be set to main the longest possibleduration in such an instance. After index i has been determined, themethod proceeds to step 240.

At step 240, the UE will update the neighbor cell search parameters. Inone embodiment, the UE will use the index value of i as determined perstep 238 to update the neighbor cell search parameters. The searchparameters NCSDUR, RSRQ_(low), and RSRQ_(high) are updated usingEquation (1), Equation (2), and Equation (3) respectively. By updatingthe neighbor cell search parameters, the duration of the neighbor cellsearch is modified as well as updating the threshold values indicatingwhen another adjusting of the cell search duration may be required. Thusby updating the neighbor cell search duration, the present disclosureadvantageously ensures a minimal level of reliability in cellidentification while reducing power consumption by avoidingunnecessarily long cell search durations. After the neighbor cell searchparameters have been updated, the UE may proceed back to step 234.

Proceeding to step 242, the UE will determine if the physical layermeasurements are within a second threshold. In one exemplary embodimentthe measured RSRQ is compared against the value of RSRQ_(high). If RSRQis less than RSRQ_(high), it is an indication that the RSRQ has notimproved sufficiently enough to change the neighbor cell search to ashorter duration causing the method to proceed to step 248. If the RSRQis greater than RSRQ_(high), the RSRQ is deemed to be of sufficientquality to decrease the neighbor cell search duration window whilemaintaining a determined level of reliability in cell identification.After the determination that RSRQ is greater than RSRQ_(high), themethod proceeds to step 244.

At step 244 of method 230, the UE will determine where the physicallayer measurement is located within the second set of thresholds. In oneembodiment, the UE searches the set of RSRQ_Threshold_(high) to findindex i that satisfies Equation (5).RSRQ_Threshold_(high)(i)<RSRQ≦RSRQ_Threshold_(high)(i−1)  (Equation 5)

By searching the set of RSRQ_Threshold_(high) values, the UE candetermine how many thresholds have been exceeded by the high RSRQmeasurement in order to properly update the neighbor cell searchduration window. If no value of i satisfies Equation (5), it is anindication RSRQ is larger than the largest value ofRSRQ_Threshold_(high). In such an instance, index i is determined to bethe highest RSRQ_Threshold_(high) value which is i=0. After the value ofindex i has been determined, the method proceeds to step 246.

At step 246, the UE will update the neighbor cell search parameters. Inone embodiment, the UE will use the index value of i as determined perstep 244 to update the neighbor cell search parameters. The searchparameters NCSDUR, RSRQ_(low), and RSRQ_(high) are updated usingEquation (1), Equation (2), and Equation (3) respectively. After theneighbor cell search parameters have been updated, the UE may proceedback to step 234.

At step 248, after a determination that the physical channel measurementwere not within a first threshold (per step 236) and not within a secondthreshold (per step 242), the UE does not update the neighbor cellsearch parameters. In one embodiment, the UE will reuse the storedvalues of NCSDUR, RSRQ_(low), and RSRQ_(high) and then proceed back tostep 234.

In an alternate embodiment, the UE retains the last used value of indexi and reinitializes NCSDUR, RSRQ_(low), and RSRQ_(high) using Equation(1), Equation (2), Equation (3) respectively. After the aforementionedparameters have been reinitialized, the UE may proceed back to step 234.

Exemplary Neighbor Cell Search Duration Operation

Consequently, in one exemplary aspect of the present disclosure, ascheme for improving the neighbor cell search procedure is disclosedthat adaptively adjusts the relevant parameter(s) (e.g., neighbor cellsearch duration) based on measured physical channel characteristics.While existing solutions for the neighbor parameters (e.g., cell searchdurations) are based on predetermined timers, one exemplary embodimentof the present disclosure adaptively adjusts the neighbor cell searchduration based on key performance metrics such as reference signalreceive power (RSRP), received signal strength indication (RSSI), signalto interference and noise ratio (SINR), and received block error rate(BLER) of the serving BS, as well as the SNR of primary synchronizationsequence (PSS) and the secondary synchronization sequence (SSS) fromboth the serving BS as well as previously detected neighbor cells.

Before addressing the specifics of adaptive neighbor cell search,various components and procedures useful in conjunction with variousembodiments of the present disclosure are now discussed in greaterdetail.

Discontinuous Reception and Transmission (DRX/DTX)

The Enhanced NodeB (eNB) of the present disclosure controls DRXoperations using various timers and/or parameters that are communicatedto the user equipment (UE). As a brief aside, LTE communications areconducted according to a time schedule that includes frames, subframes,and slots. One such exemplary LTE frame 400 is illustrated in FIG. 4.

When the UE has a radio resource connection, the UE can be allocated oneor more time slots for communication. If a UE is enabled for DRXoperation in RRC connected mode, the UE will wake-up and sleep inaccordance with its resource allocations. During RRC idle mode, the UEdoes not have a radio resource connection. The UE will periodicallywake-up to see if it is being paged within a frame of data. If the framedoes not have a page for the UE, the UE will go back to sleep.

In connected mode DRX (DRX performed during the RRC_CONNECTED state), aDRX inactivity timer indicates the time in number of consecutivesubframes to wait before enabling DRX.

Additionally, DRX operation is split into short cycles and long cycles.Short DRX cycles and long DRX cycles allow the eNB to adjust the DRXcycles based on ongoing application activity. For example, a UE mayinitially be placed in a short DRX cycle during brief lulls in activity.A DRX short cycle timer determines when to transition to the long DRXcycle; i.e., if the DRX short cycle timer expires without any UEactivity, the UE transitions to the long DRX cycle which further reducespower consumption.

If no new packets are transmitted for an extended period of time aftersuccessfully receiving a packet (unsuccessful packet reception indicatesa fading/broken connection which is handled with recovery/reconnectionprocedures), the eNB may release the RRC connection. Once the UEtransitions into RRC IDLE state, idle mode DRX is enabled.

In idle mode DRX (DRX performed during the RRC_IDLE state), an ONduration timer determines the number of frames the UE can sleep throughbefore reading the downlink (DL) control channel. Commonly used valuesfor the ON duration timer are 1, 2, 3, 4, 5, 6, 8, 10, 20, 30, 40, 50,60, 80, 100, and 200. During idle mode DRX, the UE only needs to monitorone paging occasion (PO) per DRX cycle, which is one subframe. The idleDRX cycles are 320 ms, 640 ms, 1.28 s, and 2.56 s.

Cell Search and Selection

Before neighbor cell measurements can be made, the UE needs to detectand synchronize to the neighbor cells by acquiring the knownsynchronization sequences that are transmitted periodically from theeNBs. In LTE, there are two synchronization sequences that aretransmitted; the primary synchronization sequence (PSS) and thesecondary synchronization sequence (SSS).

Now referring to FIG. 4A, a radio frame structure showing theconfiguration of the synchronization signals is illustrated. The PSS 402is formed by a frequency domain Zadoff Chu sequence with specified rootindices. The PSS specifies the Physical Layer ID of the cell. The PSS istransmitted in last OFDM symbol of the first time slot of the firstsubframe (i.e. subframe 0). The location of the PSS enables the UE toacquire the slot boundary independent from the cyclic prefix. In theexemplary illustration, the PSS is transmitted twice per radio frame andis repeated in subframe 5 (i.e. slot 10). By transmitting the PSS insubframe 0 and 5, the PSS is separated by a half frame thus enabling theUE to synchronize on the 5 ms basis of the half frame. After the UEdetermines the 5 ms timing, the UE proceeds to determine the radio frametiming and the cell's group identity via the SSS 404.

The SSS has a 5 ms periodicity and is transmitted in the symbol beforethe PSS. The SSS is formed by interleaving two binary sequences in thefrequency domain. In LTE, the SSS consists of 168 different sequences toidentify the physical layer cell identity group. By ascertaining thephysical layer identity, of the PSS, and the cell identity group, of theSSS, the physical layer cell identity can be determined to identity aparticular eNB.

Referring now to FIG. 5, FIG. 5 illustrates an exemplary correlationmechanism 500 for determining a cell's identification. In a mobilewireless channel, the received signal level may be adversely impacteddue to fading. Thus, in order to improve the reliability of detection,the UE can use PSS/SSS samples from one or more half-frames to acquirethe synchronization to use the time diversity present in fadingchannels. Increasing the number of half-frames for acquisition improvesthe reliability of detection. However, increasing the number ofhalf-frames may also increase the duration of the UE's DRX wake-up timeand thus increases power consumption.

At block 502, PSS correlation is performed on input samples receivedfrom the periodic eNB transmissions. The PSS correlation provides atiming estimate based on the 5 ms periodicity of the PSS transmission inorder to determine a synchronization timing offset. In addition, the PSSPhysical Layer ID of the eNB is derived from the input sample(s). Atblock 504, the synchronization timing offset is used to adjust the inputsample timing. By adjusting the input sample timing, a Fast FourierTransform (FFT) may be performed at block 506, in order to derive theSSS of the input sample. At block 508, multiple SSS samples arecorrelated in order to derive the Cell Identity Group value. After boththe Physical Layer ID and Cell Identity Group have been determine, thephysical cell identity can be computed in block 510.

Example Operation

During neighbor cell search and selection, increasing the neighbor cellsearch duration my increase both reliability of the detection andacquisition of a cell as well as the wake time in DRX. Since theobjective of neighbor cell search is to detect neighbors to eventuallyreselect/handover, the reliability of detecting neighbor cells becomesmore critical in scenarios where this is a high probability ofrelatively strong neighbor cells which have similar receive signalstrength as the serving cell. Hence in the scenarios where there is alow probability of having neighbor cells, the search and correspondingawake time can be kept at a minimum, or that the neighbor cell searchcan be turned off all together. Thus, it is important to be able to havea means to predict how likely it is that neighbor cells are present in agive situation.

It is recognized that in certain embodiments or implementations,physical layer metrics of a wireless channel may provide a goodindication of how likely a neighbor cell may be present. For instance,if the reference signal receive power (RSRP) of the serving BS is verylow, it is a possible indication that neighbor cells are present. Forexample, if a serving BS has a very low reported RSPR, the UE should beable to find a new cell to camp on with better RSRP or the serving BSshould have initiated a handover decision to cell with a better RSRPassuming on an adequately designed cellular network. Furthermore, ifthere is a high level of received signal strength indication (RSSI) ascompared to RSRP, it is an indication that the large amount ofinterference can be attributed to the presence of a neighbor cell(s). Asreceived signal received quality (RSRQ) is a ratio of RSRP as comparedto RSSI, RSRQ provides a good indication of the presence of neighborcells. In addition, if the received signal to interference and noiseratio (SINR) is low and the RSRP is significantly large, then there is astrong likelihood the neighbor cells are deteriorating the SINR.Additionally, if the received block error rate (BLER) is large in ascenario where the modulation and coding schemes are robust, and theRSRP is large, it is a strong indication that neighbor cells arecreating interference to deteriorate received performance.

The wireless mobile cellular channel allows for a large number ofscenarios where a number of the aforementioned conditions may occur.Hence, an adaptive algorithm can use the physical layer metrics todetermine the duration of a neighbor cell search while conservingbattery life by spending minimal amount of search time when it is notnecessary. Furthermore, a combination of these physical layer metricscan help in optimizing the search time. In instances of a highprobability of neighbor cells, such as in the cases of poor signalquality of a serving BS (e.g. very low RSRP, or BLER with high RSRP) ofhigh interference, the search window may be increased to improvereliability of detecting neighbor cells. In instances where there is alow probability of neighbor cell (e.g. low interference conditions), thesearch window can be kept small as increased reliability is unnecessary.

Referring now to FIG. 6, an exemplary generalized 600 method forimproving power consumption during discontinuous reception usingmultiple physical channel metrics is shown and described. In one aspect,the method analyzes the quality of first metrics transmitted by neighborcells and the serving BS, as well as one or more quality-relatedparameters from the serving BS.

At step 602, the UE initializes neighbor cell search parameters usefulin adaptively adjusting the neighbor cell parameters (such as e.g.,search duration, as in the example of FIG. 2 a).

At step 604, the UE obtains physical layer metrics associated with aserving BS and any neighbor cells. After all the necessary measurementsand any calculations have been performed, the method proceeds to step606.

At step 606 of method 600, the UE determines if the quality of the firstmetrics (e.g., identification sequence) meets a first criterion. If thecriterion/criteria is satisfied, the method proceeds to step 608; if notsatisfied, the method proceeds to step 610.

At step 608, negative effects on the reliable detection of neighborcells due to interference is determined to be likely, and the relevantparameter(s) updated. After the neighbor cell parameters have beenupdated, the method may proceed back to step 604.

At step 610, the UE will determine if the physical layer measurementsmeet second criteria. If the criterion is not met, it is an indicationthat reliability of indentifying neighbor cells may be compromised usingthe current neighbor search parameter(s), and that the parameter(s)should be adjusted to provide adequate reliability. The necessaryadjustment is determined in step 612.

At step 612, the UE will determine if the physical layer measurementmeets a third criterion, and if an adjustment is necessary. After anynecessary adjustment has been determined, the method proceeds to step614.

At step 614, the UE will update the neighbor cell search parameters.After the neighbor cell search parameters have been updated, the UE mayproceed back to step 604.

Proceeding to step 616, the UE will determine if the physical layermeasurements meet a fourth criterion. If the measurement(s) is/aredeemed to be of sufficient quality to adjust the relevant searchparameter while maintaining a determined level of reliability in cellidentification, the method proceeds to step 618.

At step 618, the UE will determine if the physical layer measurementsmeet a fifth criterion. After the relevant adjustment has beendetermined, the method proceeds to step 620.

At step 620, the UE will update the neighbor cell search parameters.After the neighbor cell search parameters have been updated, the UE mayproceed back to step 604.

At step 622, after a determination that the physical channel measurementdid not meet the second criterion (per step 610) or third criterion (perstep 616), the UE does not update the neighbor cell search parameters.

Now referring to FIG. 6 a, an exemplary implementation of the method 630for improving power consumption during discontinuous reception usingmultiple physical channel metrics of FIG. 6 is shown and described. Inone aspect, the method analyzes the quality of identification sequencestransmitted by neighbor cells and the serving BS as well as the signalquality from the serving BS. Specifically, a UE adjusts a neighbor cellsearch duration based on a physical layer measurement indicative ofinter-cell interference. In addition, a UE may adjust the neighbor cellsearch duration based on a comparison of the RSRQ measurement of theserving BS against a variety of thresholds.

At step 632, the UE initializes neighbor cell search parameters usefulin adaptively adjusting the neighbor cell search duration. A set S ofneighbor cell search durations (NCSDUR) are selected of N number ofNCSDUR arranged in ascending order from a minimum NCSDUR to a maximumNCSDUR. In addition, two sets of threshold are determined with a setsize of N−1. The first set is RSRQ_Threshold_(low) which is a set ofthresholds for determining when the neighbor cell search duration shouldbe increased. The second set is RSRQ_Threshold_(high) which is a set ofthresholds for determining when the neighbor cell search duration shouldbe decreased. Both of the aforementioned sets are arranged in descendingorder of largest value to lowest value. The UE initializes theparameters of NCSDUR, RSRQ_(low), and RSRQ_(high) in accordance withEquation (1), Equation (2), and Equation (3), respectively.Additionally, a pair of threshold parameters useful in comparing thedifference between signal-to-noise ratio (SNR) of identification signalsof a serving BS and a neighbor cell are determined. The first thresholdparameter is SNR_Threshold_(low) and the second threshold isSNR_Threshold_(high). SNR_Threshold_(low) and SNR_Threshold_(high)define a range of SNR values indicative of substantial likelihood ofinterference between the neighbor cell and the serving BS. In anexemplary variant, multiple sets of SNR_Threshold values may be definedas multiple sets of values. For example, sets of SNR_Threshold valuesmay be used based on the cell search window duration.

At step 634, the UE will obtain physical layer metrics relating to aserving BS and any neighbor cells. In one exemplary embodiment, the UEwill measure and calculate the RSRQ of the serving BS as well ascalculate the SNR of both the primary synchronization sequence (PSS) andthe secondary synchronization sequence (SSS). In addition, the UE willcalculate the PSS/SSS SNRs for any detectable neighbor cells during theneighbor cell search window. Upon determining the PSS/SSS SNRs of theserving BS (SNR_(serving)) and neighbor cells (SNR_(neighbor)), ΔSNR iscalculated in accordance with Equation (6).ΔSNR=SNR_(neighbor)−SNR_(serving)  (Equation 6)

In one variant, SNR_(serving) and SNR_(neighbor) are based solely on thePSS SNR. In an alternate variant, SNR_(serving) and SNR_(neighbor) aredetermined solely from SSS SNR. In yet another implementation,SNR_(serving) and SNR_(neighbor) are calculated based on a combinationof PSS/SSS SNRs. After all the necessary measurements and calculationhave been performed, the method proceeds to step 636.

At step 636 of method 630, the UE determines if the identificationsequence quality is within a threshold range. In one embodiment, the UEdetermines if ΔSNR is between the range SNR_Threshold_(low) andSNR_Threshold_(high). (See Equation (7))SNR_Threshold_(low)<ΔSNR<SNR_Threshold_(high)  (Equation 7)As discussed supra, SNR_Threshold_(low) and SNR_Threshold_(high) definea range which indicates a probability of a neighbor cell and a servingBS are substantially interfering with each other based on a similarlevel of signal strength. A ΔSNR which is lower than theSNR_Threshold_(low) is an indication the signal from the serving BS ismuch stronger than the neighbors, or if the neighbors are too far todetect causing the signal strength of the neighbors to be too weak toconsider for measurements. On the other hand, when ΔSNR is larger thanSNR_Threshold_(high), there is an indication that the neighbor cell issufficiently stronger signal than the serving BS, increasing theprobability of reliably detecting the neighbor cell. Thus the neighborcell search duration may possibly be decreased while maintain therequisite reliability in detecting neighbors. If ΔSNR satisfies thecondition of Equation (7), the method proceeds to step 638. If ΔSNR doesnot satisfy Equation (7), the method proceeds to step 640.

Proceeding to step 638, the SNR between a neighbor cell and serving BShas been determined to be too close in regards to signal strength,therefore negatively effecting reliable detection of neighbor cells dueto interference. In one embodiment, the UE will update the NCSDUR to thelongest possible search duration in an effort to increase reliability ofdetection. Thus Equation (1) will set NCSDUR with i=N (i.e. the largestduration) while RSRQ_(low) and RSRQ_(high) will be set in accordancewith Equation (2) and Equation (3) using i=N−1 (i.e. the smallestthreshold values). After the neighbor cell search parameters have beenupdated, the method may proceed back to step 634.

At step 640, the UE will determine if the physical layer measurementsare within a first threshold. In one exemplary embodiment, the measuredRSRQ is compared against RSRQ_(low). If the RSRQ is a larger value thanthe RSRQ_(low) threshold value, no increase in the neighbor cell searchduration is required and the method proceeds to step 646. If the RSRQ isbelow RSRQ_(low), it is an indication that reliability of indentifyingneighbor cells may be compromised using the current neighbor search cellduration and that the duration should be increased to provide adequatereliability. The increase in neighbor cell search duration is determinedin step 642.

At step 642, the UE will determine if the physical layer measurement islocated within in the first set of a range of thresholds. In oneembodiment, the UE searches the set of RSRQ_Threshold_(low) to findindex i that satisfies Equation (4). If no value of i satisfies Equation(4), it is an indication that RSRQ is lower than lowestRSQP_Threshold_(low) value, thus i is set to the lowest possibleRSQP_Threshold_(low) which is i=(N−1). Note that the NCSDUR will be setto main the longest possible duration in such an instance. After index ihas been determined, the method proceeds to step 644.

At step 644, the UE will update the neighbor cell search parameters. Inone embodiment, the UE will use the index value of i as determined perstep 642 to update the neighbor cell search parameters. The searchparameters NCSDUR, RSRQ_(low), and RSRQ_(high) are updated usingEquation (1), Equation (2), and Equation (3) respectively. After theneighbor cell search parameters have been updated, the UE may proceedback to step 634.

Proceeding to step 646, the UE will determine if the physical layermeasurements are within a second threshold. In one exemplary embodimentthe measured RSRQ is compared against the value of RSRQ_(high). If RSRQis less than RSRQ_(high), it is an indication that the RSRQ has notimproved sufficiently enough to change the neighbor cell search to ashorter duration causing the method to proceed to step 622. If the RSRQis greater than RSRQ_(high), the RSRQ is deemed to be of sufficientquality to decrease the neighbor cell search duration window whilemaintaining a determined level of reliability in cell identification.After the determination that RSRQ is greater than RSRQ_(high), themethod proceeds to step 648.

At step 648, the UE will determine if the physical layer measurementsare located within the second set of thresholds. In one embodiment, theUE searches the set of RSRQ_Threshold_(high) to find index i thatsatisfies Equation (5). If no value of i satisfies Equation (5), it isan indication RSRQ is larger than the largest value ofRSRQ_Threshold_(high). In such an instance, index i is determined to bethe highest RSRQ_Threshold_(high) value which is i=0. After the value ofindex i has been determined, the method proceeds to step 650.

At step 650, the UE will update the neighbor cell search parameters. Inone embodiment, the UE will use the index value of i as determined perstep 618 to update the neighbor cell search parameters. The searchparameters NCSDUR, RSRQ_(low), and RSRQ_(high) are updated usingEquation (1), Equation (2), and Equation (3) respectively. After theneighbor cell search parameters have been updated, the UE may proceedback to step 634.

At step 652, after a determination that the physical channel measurementwhere not within a first threshold (per step 640) and not within asecond threshold (per step 646), the UE does not update the neighborcell search parameters. In one embodiment, the UE will reuse the storedvalues of NCSDUR, RSRQ_(low), and RSRQ_(high) and then proceed back tostep 644.

Apparatus

Referring now to FIG. 7, an exemplary user device apparatus 700 withenhanced power consumption during discontinuous reception isillustrated. While one specific device configuration and layout is shownand discussed herein, it is recognized that many other configurationsmay be readily implemented by one of ordinary skill given the presentdisclosure, the apparatus 700 of FIG. 7 being merely illustrative of thebroader principles of the present disclosure.

The apparatus 700 of FIG. 7 includes one or more radio transceivers 702,a computer readable memory 704, and a processing subsystem 706.

The processing subsystem 706 includes one or more of central processingunits (CPU) or digital processors, such as a microprocessor, digitalsignal processor, field-programmable gate array, RISC core, or pluralityof processing components mounted on one or more substrates. Theprocessing subsystem is coupled to computer readable memory 904, whichmay include for example SRAM, FLASH, SDRAM, and/or HDD (Hard Disk.Drive) components. As used herein, the term “memory” includes any typeof integrated circuit or other storage device adapted for storingdigital data including, without limitation, ROM. PROM, EEPROM, DRAM,SDRAM, DDR/2 SDRAM, EDO/FPMS, RLDRAM, SRAM, “flash” memory (e.g.,NAND/NOR), and PSRAM. The processing subsystem may also compriseadditional co-processors, such as a dedicated graphics accelerator,network processor (NP), or audio/video processor. As shown processingsubsystem 706 includes discrete components; however, it is understoodthat in some embodiments they may be consolidated or fashioned in a SoC(system-on-chip) configuration.

The processing subsystem 706 is adapted to receive one or more datastreams from a radio transceiver 702. The radio transceiver in thisexemplary embodiment generally comprises a cellular radio transceiverwith one or more components with the ability to adjust the neighbor cellsearch duration.

Myriad other schemes for adaptive neighbor cell search duration will berecognized by those of ordinary skill given the present disclosure. Itwill be appreciated that while certain features of the presentdisclosure are described in terms of a specific sequence of steps of amethod, these descriptions are only illustrative of the broader methodsof the disclosure, and may be modified as required by the particularapplication. Certain steps may be rendered unnecessary or optional undercertain circumstances. Additionally, certain steps or functionality maybe added to the disclosed embodiments, or the order of performance oftwo or more steps permuted. All such variations are considered to beencompassed within the present disclosure is disclosed and claimedherein.

While the above detailed description has shown, described, and pointedout novel features of the present disclosure as applied to variousembodiments, it will be understood that various omissions,substitutions, and changes in the form and details of the device orprocess illustrated may be made by those skilled in the art withoutdeparting from the present disclosure. The foregoing description is ofthe best mode presently contemplated of carrying out the disclosure.This description is in no way meant to be limiting, but rather should betaken as illustrative of the general principles of the disclosure. Thescope of the disclosure should be determined with reference to theclaims.

What is claimed is:
 1. A mobile device configured to operate in adiscontinuous reception mode, the mobile device comprising: a processor;at least one wireless interface in data communication with theprocessor; logic in data communication with the processor and the atleast one wireless interface, the logic configured to: obtain aplurality of physical layer metrics of a serving base station and of oneor more neighbor cells; compare a first metric of the obtained pluralityof physical layer metrics against a current first and second thresholdsof a plurality of respective first and second sets of thresholds of theplurality of neighbor cell search parameters; and in response todetermining that the first metric is outside of the first and secondthresholds, update the current first and second thresholds to new firstand second thresholds of the plurality of first and second sets ofthresholds and adjust a neighbor cell search duration parameter to avalue corresponding to the new first and second thresholds.
 2. Themobile device of claim 1, wherein updating the current first and secondthresholds comprises: when the first metric is below the first currentthreshold: searching the plurality of first and second sets ofthresholds for a new current first threshold based on the first metric;updating the current first threshold with the new current firstthreshold; and updating the current second threshold based on an indexvalue associated with the new current first threshold; when the firstmetrics exceed the second current threshold: searching the second set ofthresholds for a new current second threshold based on the secondmetrics; updating the current second threshold with the new currentsecond threshold; and updating the current first threshold based on anindex value associated with the new current second threshold.
 3. Themobile device of claim 2, wherein the neighbor cell search duration isadjusted based at least in part on the index value.
 4. The mobile deviceof claim 1, wherein at least one of the plurality of physical layermetrics is determined from received synchronization signals receivedfrom the one or more neighbor cells and the serving base station.
 5. Themobile device of claim 1, wherein the first metric comprise a referencesignal receive quality (RSRQ) measurement of the serving base station.6. The mobile device of claim 1, wherein the logic is further configuredto: compare second metrics of the obtained plurality of physical layermetrics against a criteria range; wherein adjusting the neighbor cellsearch duration is performed based on comparing the second metricsagainst the criteria range.
 7. The mobile device of claim 6, whereincomparing the first metric against the current first and secondthresholds is performed in response to the second metrics being withinthe criteria range.
 8. The mobile device of claim 6, wherein the secondmetrics comprise signal-to-noise ratios (SNR) of received identificationsignals from the serving base station and the one or more neighborcells.
 9. The mobile device of claim 1, wherein the logic is furtherconfigured to: adjust the neighbor cell search duration based onobtained second metrics of the plurality of physical layer metricsexceeding or falling below a criteria range.
 10. A method for adaptivelymanaging a parameter of a mobile device, the method comprising:obtaining a plurality of physical layer metrics of a serving basestation and of one or more neighbor cells; comparing a first metric ofthe obtained plurality of physical layer metrics against a current firstand second thresholds of a plurality of respective first and second setsof thresholds of the plurality of neighbor cell search parameters; andin response to determining that the first metric is outside of the firstand second thresholds, updating the current first and second thresholdsto new first and second thresholds of the plurality of first and secondsets of thresholds and adjust a neighbor cell search duration parameterto a value corresponding to the new first and second thresholds.
 11. Themethod of claim 10, wherein updating the current first and secondthresholds comprises: when the first metric is below the first currentthreshold: searching the plurality of first and second sets ofthresholds for a new current first threshold based on the first metric;updating the current first threshold with the new current firstthreshold; and updating the current second threshold based on an indexvalue associated with the new current first threshold; when the firstmetrics exceed the second current threshold: searching the second set ofthresholds for a new current second threshold based on the secondmetrics; updating the current second threshold with the new currentsecond threshold; and updating the current first threshold based on anindex value associated with the new current second threshold.
 12. Themethod of claim 11, wherein the neighbor cell search duration isadjusted based at least in part on the index value.
 13. The method ofclaim 10, wherein at least one of the plurality of physical layermetrics is determined from received synchronization signals receivedfrom the one or more neighbor cells and the serving base station. 14.The method of claim 10, wherein the first metric comprise a referencesignal receive quality (RSRQ) measurement of the serving base station.15. The method of claim 10, further comprising: comparing second metricsof the obtained plurality of physical layer metrics against a criteriarange; wherein adjusting the neighbor cell search duration is performedbased on comparing the second metrics against the criteria range. 16.The method of claim 15, wherein comparing the first metric against thecurrent first and second thresholds is performed in response to thesecond metrics being within the criteria range.
 17. The method of claim15, wherein the second metrics comprise signal-to-noise ratios (SNR) ofreceived identification signals from the serving base station and theone or more neighbor cells.
 18. A non-transitory computer readablemedium comprising a plurality of instructions for adaptively managing aneighbor cell search duration of a mobile device, the plurality ofinstruction that, when executed, are configured to cause the mobiledevice to: obtain a plurality of physical layer metrics of a servingbase station and of one or more neighbor cells; compare a first metricof the obtained plurality of physical layer metrics against a currentfirst and second thresholds of a plurality of respective first andsecond sets of thresholds of the plurality of neighbor cell searchparameters; and in response to determining that the first metric isoutside of the first and second thresholds, update the current first andsecond thresholds to new first and second thresholds of the plurality offirst and second sets of thresholds and adjust a neighbor cell searchduration parameter to a value corresponding to the new first and secondthresholds.
 19. The non-transitory computer readable medium of claim 18,wherein updating the current first and second thresholds comprises: whenthe first metric is below the first current threshold: searching theplurality of first and second sets of thresholds for a new current firstthreshold based on the first metric; updating the current firstthreshold with the new current first threshold; and updating the currentsecond threshold based on an index value associated with the new currentfirst threshold; when the first metrics exceed the second currentthreshold: searching the second set of thresholds for a new currentsecond threshold based on the second metrics; updating the currentsecond threshold with the new current second threshold; and updating thecurrent first threshold based on an index value associated with the newcurrent second threshold.
 20. The non-transitory computer readablemedium of claim 18, wherein the instructions are further executed to:compare second metrics of the obtained plurality of physical layermetrics against a criteria range; wherein adjusting the neighbor cellsearch duration is performed based on comparing the second metricsagainst the criteria range.